The crystal and molecular structures of derivatives of colchicine will be dtermined by X-ray diffraction. Detailed comparisons of molecular goemetry will be made to attempt to find correlations with antitumor, antigout and antimitotic behavior of these drugs. Compounds to be studied include colchicine and derivatives of thiocolchicine. BIBLIOGRAPHIC REFERENCE: T.N. Margulis, "X-ray Analysis in Microtuble Inhibitors," in M. Borgers and M. de Brabander ed., Microtubules and Microtubule Inhibitors, 1976, North-Holland, Amsterdam, p. 67-78.